The present invention relates to a method and a device for processing plastic articles, in particular articles of elongate shape such as pipes, enabling these articles to be reduced into small-sized fragments, so as subsequently to classify these fragments according to their nature.
The recycling of plastic articles nowadays constitutes a particularly important activity for the producers of these articles. One of the problems which arise during recycling is the classification of the various plastics collected; indeed, the possibility of reusing them is directly related to their purity, which depends directly on the quality of the classification.
Within this framework, various solutions have already been proposed. Thus, in Patent Application NL 9,101,705, an installation is described for recycling plastic articles which essentially comprises a crusher and a screen. The crusher subjects the articles to be processed to violent impacts, which reduces them to pieces whose smallness decreases with the brittleness of their constituent material. Screening therefore enables the fragments to be classified according to their size and therefore, indirectly, according to the nature of the constituent material of the processed article.
However, this known technique has many drawbacks. Indeed, some plastics, such as, especially, rubber, polyethylene (PE) and polypropylene (PP), are difficult to crush compared to others, such as, for example, polyvinyl chloride (PVC). In the case of not very brittle plastic articles, for example in the case of polyethylene pipes, this known method does not work very well and rapidly leads to blockage of the crusher, which fails to shatter the articles. This risk of blockage is increased particularly if the articles to be processed consist of a plastic reinforced by means of reinforcing fibres, for example glass fibres. Consequently, it is understood that, in order for it to operate correctly, this known method must necessarily be preceded by a prior step of manually sorting the articles, which step constitutes a significant disadvantage thereof.
Furthermore, this known method is difficult to apply to large-sized articles : it is, for example, impossible to introduce, into a normal-sized crusher, pipes of 6 m in length, which, however, constitutes a standard length for pipes. In this case a prior step of cutting up the pipes is necessary, unless a crusher of exceptional size is used. Both these solutions are disadvantageous from the economic standpoint.
An additional disadvantage of this known method is the high noise level which it generates.